Lessons Learned from Field Monitoring of Instrumented Piled-Raft Bearing in Rock Layer

Piled rafts are increasingly used for various structures due to the enhanced load-carrying capabilities of raft and piles combined as a single structural unit. In this study, an experimental testing program using a full-scale, fully instrumented piled raft was established and field monitoring was carried out. Test results from the field monitoring were presented and analyzed. It was found that various factors affected the measured load-carrying behavior of the piled raft, including those that were not identified and considered in the design. The measured load-transfer curves of the piles showed an increase in axial load with depth within the upper soil zone, which was different from those assumed in the design and commonly observed from axially loaded piles. Factors that contributed to such unusual load-carrying behavior were the subsoil-layer condition, design modification, and the adequacy of the construction procedure. Results from the finite-element analysis confirmed that inclined soil-layer and loading conditions could cause loads that became unevenly and asymmetrically distributed on piles of an axially loaded piled raft with variations in the load-transfer relationship.